Sheet member for conforming component leads to printed circuit board holes



Feb. 15, 1966 LLER ETAL 3,235,345

CONFORMING COMPONENT CIRCUIT BOARD HO D E T m mo M 5 T E EA H S 7 V" l HJ d e l .1 F l a n i g i r 0 LBS 2 Sheets-Sheet 1 INVENTOR. GLENwooD H.FULLER ROBERT U Rossn'aR LLMRN R. Pen-ER TAL NG COMPONENT CIRCUIT BOARDHO G. A. FULLER E MEMBER R CONFORMI TO PRIN 5 Feb. 15, 1966 SHEET LEADSOriginal Filed July 7, 195

LES

2 Sheets-Sheet 2 I INVENTOR. GLENwooD H. FULLER RQBERT ULL MAN RossVYERR. POTTER United States Patent SHEET MEMBER FOR CONFORMING COMPO- NENTLEADS TO PRINTED CIRCUIT BOARD HOLES Glenwood A. Fuller, Hershey, andRobert Ullman and Rossiter R. Potter, Harrisburg, Pa., assignors to AMPincorporated, Harrisburg, Pa.

Original application July 7, 1955, Ser. No. 520,544, now Patent No.3,185,952, dated May 25, 1965. Divided and this application July 23,1962, Ser. No. 211,912

2 Claims. (Cl. 29-1835) This is a division of application Serial No.520,544, filed July 7, 1955, now Patent No. 3,185,952, granted on May25, 1965.

This invention in general pertains to electrical connections and moreparticularly in relation to printed electrical circuit boards, themethod of connecting electrical components and the like to such boardsand the connection thus formed.

In the art of manufacturing electronic assemblies or sub-assemblies byemploying printed circuitry, the usual method of mounting electricalcomponents and jumper leads to the circuitry board has been merely tofix the components to the panel by threading the component leads throughthe circuit board holes and bending or clinching the lead ends so as tofasten the component tightly against the circuit board surface. With thecomponent thus clinched, the board is then dipped in a bath of moltensolder whereby to reinforce the mechanical and electrical connectionwith solder. In connecting the ends of jumper leads to the board, thestripped ends of such leads commonly are threaded through appropriateholes and bent so that during the solder-dipping operation theinsulation of the lead provides the necessary support on the top surfaceof the board.

Certain inherent disadvantages, however, stem from mounting componentstightly against the face of the board. Poor circulation of air for thosecomponents, such as resistors, which tend to become heated in operationmay result in component failure due to overheating. Moreover, for thoseboards which include printed circuitry on both faces, it is undesirableto have resistive components, being a source of heat, in direct contactwith the more or less delicate metallic strips forming the printedcircuitry.

In the connection of jumper leads it is especially important to providea mechanical connection which has a high resistance to pushing, pullingor twisting without relying on the bond between the underlying copperstrip and the surface of the dielectric forming the body of thecircuitry board. Any stresses placed on the jumper lead, when connectedby the conventional method, which may occur during assembly of theboards or through maintenance and testing of the electronic units formedthereby result in a direct strain on the copper bond of the printedcircuit. Unless great care is taken, these stresses will result instripping the copper from the face of the board.

Accordingly, it is an object of the present invention to provide animproved means and method for mounting electrical components to printedcircuit boards.

Another object is to provide a means for mounting in spatial dispositioncomponents on printed circuit boards with a mechanical connectionbetween the lead wires of the component and the board that leadsstability to the connection both prior and subsequent to anysolder-dipping operation.

A further object is to provide a method for adapting component leads ofa range of diameters to a uniform size, permitting standardization ofthe circuit board holes.

Still another object is to provide an adapter for electrical componentswhich produces a uniform and reliable mechanical connection with a givensize circuitry board hole throughout a relatively wide range of holediameters as permitted by design tolerances.

A still further object is to provide an adapter for component leadsespecially designed to enhance the flow of solder, through capillaryaction, up through the hole and around the component lead during thesolder-dipping stage of circuitry board assembly.

Yet another object is to provide an adapter for electrical componentleads which, upon insertion into a circuit board hole, leaves apredetermined maximum void space without reducing the mechanicalstability of the connection.

Still another object is to provide an adapter for component leads whichfacilitates the insertion of the leads within circuit board holes byautomatic fitting machines in a mechanized assembly line.

These objects are, in general, attained by imparting a cuneateconfiguration of special design to the end portions of the componentleads. Conveniently, such configuration may be obtained by cold-forgingor crimping about the component lead ends a pre-formed sheet metaladapter which is, according to one embodiment of the present invention,generally U-shaped in cross-section and includes a trough from opposedside edges of which respectively extend a pair of upstanding earsadapted to be forced during crimping into tight engagement with at leasta portion of the component lead. The adapter may be applied, forexample, by crimping or shaping dies having die faces which convergetoward the end of the lead so that for leads of varying diameter more orless of the metal composing the adapter and lead is extruded away fromthe lead end, thus forming the end portion of the lead to precisely auniform cross-section, independent of the original diameter of the lead,and tapering to a point substantially coaxial with the axis of thecomponent lead. The free ends of the upstanding ears of the connectormay be curled or deformed, if desired, about a tight radius leaving aspace between the opposed inwardly curled ear faces between which anindentor may pass to form a groove in a wire. Upon insertion of theformed lead end in a circuit board hole, the wire groove, supplementedin part by the curled ears of the adapter and in part by the side wallsof the hole, forms a capillary tube thorugh which solder readily flows.In its final form the lead end portion is substantially rectangular incross-section with the bottom side edges being relatively sharp so as tomake firm contact with the side walls of the circuit board hole inaccordance with the taper whereby to achieve a good mechanicalconnection.

Other objects and attainment of the present invention will becomeapparent to those skilled in the art upon a reading of the followingdetailed description when taken in conjunction with the drawings inwhich there are shown and described several embodiments; it is to beunderstood, however, that these embodiments are not intended to beexhaustive nor limiting of the invention but are given for purposes ofillustration in order that others skilled in the art may fullyunderstand the invention and the principles thereof and the manner ofapplying it in practical use so that they may modify it in variousforms, each as may be best suited to the conditions of a particular use.

In the drawings:

FIGURE 1 is a perspective view of the end portion of an electricalcomponent lead formed in accordance with one embodiment of the presentinvention;

FIGURE 2 is a perspective view of a plurality of adapter members instrip form prior to their application to component leads to produce thelead end portion shown in FIGURE 1;

FIGURE 3 is a fragmentary sectional plan view illustrating the mountingof the lead end portion of FIGURE 1 in a hole of a printed circuitboard;

FIGURE 4 is a diagrammatic side view of an electrical component mountedon a printed circuit board during dipping of the board in a moltensolder bath;

FIGURE 5 is a fragmentary view in elevation of a printed circuit boardillustrating the mounting in a circuit board hole of a lead end portionaccording to another embodiment of the invention prior to soldering theconnection;

FIGURE 6 is an enlarged view generally taken at lines 66 of FIGURE 5,but subsequent to soldering the connection;

FIGURE 7 is a view generally taken along lines 7-7 of FIGURE 6 andillustrating the formation of solder fillet in connection with the leadend portion shown in FIGURE 5;

FIGURE 8 is an elevational view of pro-formed adapter blanks in stripform which may be utilized to produce the lead end portion of FIGURE 5;

FIGURE 9 is a perspective view of a pre-formed blank shown in FIGURE 8;

FIGURE 10 is a perspective view of the adapter member shown in FIGURE 9applied to the end portion of an electrical component lead;

FIGURE 11 is an exploded perspective view of the dies for crimping theembodiment of the adapter member shown in FIGURES 8 and 9;

FIGURE 12 is a sectional side view of the crimping dies of FIGURE 11assembled and in an intermediate 1stage in crimping an adapter memberabout a component cad;

FIGURE 13 is fragmentary front view showing in crosssection the crimpingdie parts of FIGURE 11 and 12;

FIGURE 14 is a perspective view of a lead end portion in accordance withanother embodiment of the present invention;

FIGURE 15 is a perspective view of an adapter member which may beutilized to produce the lead end portion of FIGURE 14; and

FIGURE 16 is a fragmentary sectional view of dies in an intermediatestage of operation for crimping the adapter of FIGURE 15.

Generally in the solder-dip method of effecting the electricalconnections between the leads of an electrical component and theconductive strips of a printed circuit panel, after application of anappropriate fiuxing agent, the component is mechanically set in thepanel by threading the leads through the holes from which the conductivestrips desired to be connected through the component radiate. As thusconnected, the underside of the panel is dipped in a. bath of moltensolder whereupon solder wicks between the lead and the side walls of thehole to provide the desired solder joint. Such operations are well knownin the art of processing printed circuit panels and they may be carriedout manually, or desirably accomplished completely automatically, e.g.,by a plurality of machines operating serially which assemble a completeelectronic subassembly from a supply of circuit panels, leads andelectrical components. Such machines typically comprise means forinitial preparation of the panels and placing them on a conveyor alongwhich is aligned a battery of machines for preparing and fitting to thepanels each of the various electrical components comprising theelectronic subassembly, the last stage in the assembly line being asolder-dipping operation.

In the following description reference will be made to the adaptation ofour invention to use with printed circuit boards or panels such as areemployed in the art of automatically pr-e-formed electrical circuitry,but it is to be understood that this application is selected by way ofexample and other applications will be apparent to those skilled in theart. Moreover, the reference to printed circuit boards specifically isnot to be taken as limiting since the invention is equally applicable tothe panels formed of any suitable dielectric material, and any method ofreproducing a circuit design on either the upper or lower surfaces, orboth, may be employed, such as by painting, spraying, chemicaldeposition, die stamping, laminating, etc.

It is desirable, especially where conductive strips are printed on bothsurfaces of the panel, that the leads of the electrical components beset in the holes of the printed circuit board in a manner to supportmechanically the body of the component away from the surface of theboard both during and subsequent to the solder-dipping stage inassembly. To provide such support, the end portion 1, FIGURE 1, of eachof the component leads is shaped to have generally a cuneateconfiguration tapering toward the tip 2 from a maximum transversedimension at least equal to the diameter of the circuitry board holewhereby the lead end portion may be mechanically locked in the hole by awedging action. As will be described in connection with FIGURE 4, leads4, typically single stranded solid wires, when bent into a U-shape andanchored at tips 2 are contemplated to have sufiicient rigidity tosupport the component body 3 off the face of board 5.

The cuneate form may conveniently be imparted to the lead ends bycold-forging thereon an adapter member 7 of a suitable malleable sheetmetal stock, the coldforging operation being performed through the useof die apparatus generally similar to conventional and wellknowncrimping apparatus for applying solderless electrical terminals andexemplified by Patent No. 2,692,422 issued October 26, 1954, to Frank L.Pierce, except that, as will be described in connection with FIGURES ll,12 and 16, a longitudinal convergence is imparted to both the operatingfaces of the die parts. Adapter members 7, as preformed blanks in FIGURE2, each may comprise a trough 9 having a pair of upstanding ears 11extending from opposed side edges, with a connecting link 13 joining apair or more of troughs in end-to-end strip fashion if desired.

Forming of adapter members 7 to the configuration shown in FIGURE 2 isaccomplished by blanking and forming techniques generally well-known inthe art, and preferably from strip stock whereby a large number ofelements may be joined as a continuous strip rolled into a reel, thus tofacilitate handling and subsequent application to component leads byautomatic or semi-automatic crimping machines as will be referred to inconnection with FIGURES 8 to 13. Prior to application of the adapters,the base metal composing the adapter strip is preferably plated with ametal, such as tin, to which solder readily adheres. In contemplation ofthe soldering operation each adapter, conveniently while still in stripform, may have applied thereto a non-corrosive flux, for example,stearic wax, which preferably also has characteristics rendering theflux capable of acting as a lubricating agent for the crimping diesduring the crimping operation. In the crimping operation lead 4 isdisposed within trough 9 and cars 11 are curled under compression aboutand inwardly toward the lead to effect an intimate contact securelyalfixing adapter 7 to the lead. Preferably the crimping die partsinclude a flat or slightly concave anvil whereby the resultant crimpwill be substantially rectangular in cross-section, FIGURE 3, havingrelatively sharp corners 13 along the bottom side edges with the uppersurfaces of ears 11 shaped to define a longitudinal groove 15 along thetop.

In addition to providing for a wedging action, tapering the crimp ofadapter 7 facilitates insertion of lead end portion 1 within thecircuitry board holes. This is especially advantageous where thecomponents are to be inserted by automatic means since the accuracyrequired of such means may be reduced proportionally with the sharpnessof tip 2. Moreover, by maintaining the crimp height, being defined bythe degree to which the die parts of the crimping apparatus are closed,the wide range of wire sizes encountered in mounting the variety ofelectrical components utilized in printed circuit applications areadvantageously reduced to a uniform size and shape at end portion 1whereby standardization and uniformity of the circuit board holes may beachieved regardless of the diameter or character of the component lead.To this end the taper angle and crimp height are set so that thesmallest diameter wire employed will just be sufiiciently gripped tofurnish adequate support for the component, and the maximum transversedimension at the rearward end of adapter 7 is greater than the holediameter with the length of adapter 7 being not significantly greaterthan the thickness of the circuitry board. For example, on astandardized 0.072 inch hole diameter, an included taper angle of 10 fora crimp 0.170 inch in length for boards in the range of 0.060 inchthickness will accommodate wire sizes from 0.020 to 0.047 inch indiameter. It will be understood, of course, that with a constant crimpheight the smallest accepted wire will be engaged by cars 11 duringcrimping only over a limited length from tip 2 along the length ofadapter 7, but as larger wire sizes are used, the effective crimp lengthwill increase until substantially a voidless crimp is had over the wholelength of the crimped area. Larger wire sizes than that in which themass of metal included within the crimp length precisely matches thevoid space within adapter 7 may be used since any excess of wire metalwill simply be extruded out of the crimp area back along the wire axisdue to crimping on a taper.

Referring again to FIGURE 3, wedging end portion 1 within hole 17 ofcircuitry board 19 causes corners 13 to bite into the sidewalls of thehole thus securely anchoring lead 4 in a manner such that stresses onthe lead or component will be absorbed in the mechanical lock affordedby adapter 7 without transmission to or reliance on the strength of thebond between conductive strips 21 and board 19 prior or subsequent tosoldering.

In thev solder-dipping operation, to promote the wicking of solderthrough capillary action and formation of solder fillets on both theupper and lower surfaces of board 19 around end portion 1, wherebyconductively to couple lead 4 with conductive strips 21, theconfiguration of end portion 1 in cross-section relative to hole 17should provide as much void area as possible without adversely affectingthe holding power of adapter 7 for the component lead. In the embodimentshown in FIGURES 1 to 3, the primary paths for the flow of solder areup-along adapter 7 between its bottom surface and the side walls of hole17, and along the top surface of adapter 7 and that portion of the sidewalls of hole 17 bounded by the tangential points of contact with curledcars 11, the closed boundaries of these paths defining capillary tubeshaving cross-sectional end areas indicated respectively at A and B inFIGURE 3.

Upon applying molten solder to the underside of the circuitry board, asby dipping the assembly in a solder bath, FIGURE 4, solder will rise incapillary tubes A' and B and on reaching the fluxed printed strip 21ringing hole 17 will spread to form after hardening into a solderfillet. Solder will also cling to and harden on the metal surfaces onthe underside of board 19 thus to form a fillet, or solder button,surrounding end portion 1 on both sides of board 19 as is shown and moreparticularly described in connection with FIGURE 7.

The method employed to crimp adapter 7 to the component lead isespecially advantageous in that groove 15, formed by inwardly curledears 11, increase the size of capillary tube B, thus enhancing the flowof solder in the solder-dip operation and ultimately the reliability ofthe electrical connection, by virtue of the solder, between lead 4 andstrip 21. In the embodiment of FIG- URES 1 to 3, however, the electricalqualities of the connection between lead 4 and strip 21 depend in largemeasure upon the effectiveness of the connection between lead 4 andadapter 7 since at best a relatively small surface area of the lead willbe in direct contact with the solder.

Preferably, end portion 1 is formed so that solder comes in contact overa substantial area with freshly exposed surfaces of lead 4 therebydirectly coupling strip 21 and lead 4. To this end, and to enhance thesolder flow characteristics of capillary tube B, in the embodimentdescribed in connection with FIGURES 5 to 10, a longitudinal passagewayor groove 23 is provided along the upper surface of the lead end portion27, FIGURE 10, which exposes lead 4 regardless of any adapter memberwhich may be formed on the lead end portion. Advantageously, theupstanding ears of an adapter member form the passageway side walls andthe component lead provides the bottom boundary, the lead preferablybeing impacted in the trough of the adapter member together with acoining action which exposes fresh metal in the bottom of the groove. Asshown, groove 23 extends substantially along the formed end of the leadwhich is coined or indented to a depth equal to approximately the centerthereof at tip 29, the groove depth tapering away from the lead axis inaccordance with the taper of end portion 27 as best shown in FIGURE 7and varying in depth of indentation according to the lead diameter ofthe component involved.

End portion 27, similar to end portion 1 of FIGURES 1 to 3, mayconveniently be formed through utilization of an adapter member 31,FIGURE 9, which, in general, comprises a trough 33 for receiving lead 4and upstanding ears 35 extending from the side edges of trough 33, ears35 being adapted to be curled inwardly toward the lead in a manner to bedescribed. Although the adapters may be separate pieces formed about theends of the component leads by hand tools with the components thereafterbeing supplied to feeding machines in the circuit board assembly line,it is contemplated that the adapters will be made in strip form, thatis, connected 1n end-to-end fashion as by links 37, FIGURE 8. As thusconnected, the adapters may be automatically fed and applied by standardapplicator machines which may be made a part of the circuit boardassembly line, such machines, except for the crimping section thereof,forming no part of the present invention and hence being omitted forpurposes of simplicity.

The crimping die section, shown in exploded view in FIGURE 11, includesan upstanding generally rectangular column or post 39 which comprisesthe die anvil, the anvil being provided with a substantially flat dieface 41 of a length slightly greater than trough 33. Post 39 projectsfrom lower die block 43 which is rigidly mounted on the fixed press bed,not shown, of the applicator machine. Upper die block 45 is providedwith a recess formed by side walls 47 which are spaced to receive column39 when the dies are being closed, FIGURE 13. The end of the recessapproximates a W configuration with smoothly rounded bottoms formed by apair of parallel cylindrical troughs 49 each of which is tangential toone of side walls 47 and which unite to form a longitudinal ridge 51along the center line of the recess. Upper die block 45 is mounted onand reciprocates with the movable ram, not fully shown, of theapplicator machine. Also mounted on the applicator ram adjacent the rearsides of upper block 45 is a slug-out plate 53 having edges 54 whichsever from the strip the leading adapter upon its being disposed in thecrimping area on die face 41.

On the front side of upper block 45 is mounted a guide plate 55 having arecess centered relative to the crimping recess and defined by Sidewalls 57 and bottom 59. Side walls 57 initially converge inwardly towardbottom 59 and serve to force leads 4 into alignment with the axis oftrough 39 as the die parts move together. Bottom 59 of the guide recessis disposed slightly in advance of the crimping recess relative to thedescent of the ram and serves to force the component lead into adaptertrough 33 just prior to crimping, this action being especiallyadvantageous where the lead diameter is near the upper end of the rangeof wire sizes accommodated. As the larger wire sizes contemplated to becrimped have a greater diameter than the diameter of adapter trough 33,the forceful insertion of the leads by guide plate 55 effects a propercrimping action by assuring that the lead enters trough 33 before theinward curling of ears 35.

In the crimping action, FIGURES 12 and 13, a feed finger 61, operatingin timed sequence with the movement of the applicator ram, advances thestrip to position the leading adapter on die face 41 prior to thedescent of die block 45. As the ram and die block 45 approach lowerblock 43, guide plate 55 positions lead 4 in trough 33 as the slug-outblade severs link 37 from between the leading pair of adapters. Furtherdescent of die block 45 initiates the curling of cars 35 around thecontour of die trough 49, ridge 51 turning the ends of ears 35 inwardly.As die block 45 continues its downward movement, ridge 51 maintains aseparation between the ends of ears 35 which are turned slightlydownwardly into lead 4. Ridge 51 effectively passes between ears 35while curling the ear ends and, in the final portion of the downwardstroke of die block 45, indents and coins lead 4 to form groove 23 andsubstantially a voidless crimp extending along the length of end portion27 to a degree depending on the diameter of lead 4. To facilitate thiscurling action the outside ends of cars 35 are preferably beveled orswaged, as at 62, in the blanking process for fashioning the preformedstrip.

The crimp, shown in cross-section in FIGURE 6, thus made results in anenlargement of capillary tube B which, on mounting the formed lead endin a circuit board hole, comprises a portion of the side walls of hole17, the ends of ears 35 and groove 23. The precise shape of tube B andgroove 23 depend, of course, on the configuration of the recess in upperforming die 45. Advantageously, troughs 49 curl ears 35 about radii ofcurvature approximately equal respectively to one-fifth of the width offormed end portion 27, ridge 51 thus also being laterally equal toone-fifth of the aforesaid width and depending from the bottom oftroughs 49 to a length slightly greater than the aforesaid width so asto indent substantially to the axis of lead 4 at the forward end of thecrimping dies. By way of example, specific dimensions for the dies andadapter member so as to accommodate a wire range of 0.020 to 0.047 inchmay be: for the dies, anvil or crimping width-0.067 inch, anvil orcrimping length0.150 inch, radius of curvature of troughs 490.013 inch,width of ridge 51 0.012 inch, height of ridge 51-0.017 inch, includedangle of die convergence-40; for adapter 31, thickness of stock0.0l4inch, radius of curvature of trough 330.016 inch, with ears 35 extending0.115 inch above the base of trough 33 and an outside divergence of0.100 inch at their ends. Similar dimensions for the embodiment shown inFIGURES 1 to 3 may be used except that troughs 49 would have a radius ofcurvature approximately equal to 27% the width of the crimp and convergeto form a sharp cusp instead of the ridge as above defined.

From the foregoing dimensions, it will be apparent that on crimpingadapter 31 about component leads having a diameter near the maximumsize, a more violent extrusion of metal, both of lead 4 and adapter 31,will occur away from the point of convergence of the tapering diesurfaces. To limit the extrusion of the metal of adapter 31 and toprevent the adapter from being forced wholly out of the crimp area,anvil 39 is provided with a lip 63 rising above the anvil surface thusforming a stop shoulder beyond which extrusion of adapter 31 may notoccur. In addition, it is desirable, especially where small size leadsare involved, that the inside surface of the adapter member be providedwith transverse serrations 64 which improve the gripping action near theforward end of the adapter thus to prevent the lead from being squeezedout of trough 33 during crimping. It is also desirable that the rear endedges of adapter 31 be crimped square, that is, after forming, the rearedges should be perpendicular to the axis of lead 4 whereby to provideflat surfaces surrounding the lead of a width equal to the stockthickness on which an insertion tool or machine may conveniently operateto force the lead end into a circuit board hole. For this purpose thetop edges of cars 35 are inclined downwardly toward the rear end oftrough 33, FIGURE 8, to avoid the tilting of adapter 31 in the crimpingdies which would tend to occur should upper die 45 first engage theadapter at the rear end of ears 35. Exemplifying, for a 10 convergenceof the dies, a 17 inclination of ears 35 will suffice to assure a squarecrimp.

With adapter 31 thus formed about the end of lead 4, capillary tube inarea and shape is adequate to insure the flow of solder in thesolder-dipping operation. In this connection it will be understood thatin designing a capillary tube, area is not the sole consideration. Along narrow slot, e.g., the openings bounded by the sides of adapter 31and the hole side walls, FIGURE 6, has proven in practice to beunreliable in flow characteristics, the narrower the tube opening theless likelihood of achieving consistently good solder connections eventhough the area of the tube when translated into a circle would besufiicient under the conditions of use. On inserting end portion 27 in ahole with the rear of the adapter substantially flush with the boardsurface, groove or passageway 23, as shown in FIGURES 6 and 7 and formedwith parts having the dimensions given above, provides a capillary tubehaving an end opening which roughly encompasses a rectangle at least0.012 inch in width and 0.025 inch in height. Such dimensions haveproven reliable under the exemplified conditions of use, a minimumworkable width being approximately 0.010 inch at the groove bottom incontact with the lead and a height of about 0.024 inch. The minimumheight and width relationships will be affected, however, by theconditions of use, that is, the solder composition as related to itsfiowability, the wetting characteristics of the solder flux, the degreeof taper of the capillary tube, etc. For example, it has been found thatthe diameter of the larger opening at the bottom of the capillary tubewhich is essentially cone-like in shape inversely affects, due either tothe physics of capillary flow or to greater entrapment of flux from thesolder bath, the minimum diameter of the small opening at the other endof the tube.

Hardening of the solder after the solder-dipping operation results inthe formation of solder fillets 65, FIGURE 7, on both the upper andlower surface of the circuit board, directly connecting lead 4 at groove23 with conductive strips 21. In this connection when the diameter oflead 4 is near the low end of the range of wire sizes, the crimping diesat the constant crimp height are effective to coin the lead only over ashort length near the lead end. In this event the opening between cars35 afforded by ridge 51 renders the interior of adapter 31, atapproximately the point where the crimp ceases to be voidless,accessible to solder which may then flow along the lead within theadapter thus assuring continuous metal-tometal contact over the lengthof lead 4 in the circuit board hole.

Upon forming of lead end portion 27, the components are contemplated tobe fed automatically to the mounting machines in the assembly line, suchmachines effecting an automatic placement of the components in theappropriate holes in the circuit boards. To allow for such machines amaximum tolerance in the accuracy of the placement operation, the tip 29of the formed lead should be as sharp as possible and coaxial with thelead. For

this purpose anvil 39 is provided with an inverted V- shaped extension67 which cooperates with a V-shaped groove 69 in slug-out blade 53 toshear link 37 from the body of adapter 31 so as to leave a V-shapedextension 71 integral with the front end of trough 33, FIGURE 10. Toarrange the apex or point of extension 71 in alignment with the axis oflead 4, the plane of extension 67 of anvil 39 is inclined slightlyupward relative to the plane of die face 41. To facilitate placement ofthe adapter body on anvil 41, that portion of link 37 in the pre-formedstrip, FIGURE 8, which is to form extension 71 is pre-bent relative totrough 33 in accordance with the inclination of anvil extension 67. Fora dimensional example, in combination with the dimensions above referredto, a 12 inclination for anvil extension 67 relative to the place of dieface 41 will align the point of a trough extension 71 having a length of0.068 inch coaxial with lead 4 and cut at an included angle of 50.Preferably the lower portions of the front edges of ears 35 are providedwith transition sections 72 which have a configuration to impart, oncrimping the adapter, a tapering U-shaped crosssection to the troughextension in the region adjacent trough 33 whereby to avoid abruptchanges in the crosssection of end portion 27 that otherwise might tendto interfere with the insertion operation.

In the embodiment shown in FIGURES through the component lead must beplaced with some accuracy within trough 33 of adapter 31 to effectoptimum crimping, that is, the end of the component lead should bedisposed near the forward edges of ears 35 in order to assure crimpingof smaller diameter wires yet must not be inserted so far as tointerfere with the formation of the pointed trough extension 71. Inautomatic application of the adapters this additionally requiresaccurate pretrimming of the leads. Advantageously, the leads are trimmedsimultaneously with the crimping operation and the accuracy of the leadinsertion rendered less critical. To these ends in the embodiment shownin FIGURES 14 to 16, the adapter member 73 is formed to permit insertionif lead 4 past the forward edges of ears 75 whereby in the shearingoperation slug-out blade 77 severs strip connecting link 79 in a mannerto form sharpened trough extension 81 and simultaneously trims lead 4 tohave a pointed end 83 as best shown in FIGURE 14. In this connection thedownward pressure exerted by slug-out blade 77 on the lead end duringtrimming is also advantageous in that in combination with guide plate85, similar in function to guide plate 55 in FIGURE 11, lead 4 ispostively forced into trough 87 from both ends of the adapter prior tocurling ear 75 during crimping regardless of the lead diameter. It willbe apparent that the most extreme extrusion and coining of metal occursat the forward end of the crimping dies. Inserting lead 4 to the extentrequired for trimming during crimping, however, adds to the metal whichmust be moved out of the critical forward portion of the dies. To reducethe mass of metal at this point the forward edges of cars 73 are notchedas at 89 adjacent trough 87.

With the end portions of component leads formed in accordance with thepresent invention it will be apparent to those skilled in the art thatthe placement of the leads within the circuit board holes is facilitatedand the flow of solder in the solder-dipping operation is enhancedresulting in a high quality mechanical and electrical connection to theboard and to the printed conductive strips, with the components beingadvantageously rigidly and spatially disposed above the surface of thecircuit board.

It will be further apparent that the provision of the longitudinalgroove in the formed lead end will promote the flow of solder bycapillary action up through the circuit board holes along the componentlead thence to contact the printed conductive strips of the surface ofthe circuit board, FIGURE 7, regardless of whether the conductive stripsare extended to cover the side walls of the circuit board holes.

Obviously the formed end may also provide the means by which printedcircuit jumpers may be mounted in the circuit board holes. Commonly,such jumpers are insulated with polyvinyl formal thermo-plastics, suchas Formvar, which heretofore had to be initially stripped beforeelectrical contact could be made with the printed strips of the board.According to the present invention, however, Formvar leads can beutilized without prior preparation since in the soldering operation thesolder will contact the wire core of the lead either at the trimmed tip,FIGURES 7, 10 and 14, or along the formed groove which, because of theviolent deformation of the lead in the crimping operation, provides anarea in which the Formvar insulation has been broken.

In addition, it will also be apparent that for lead end portions formedin accordance with the principles of the invention shown and describedin connection with FIG- URES 5 through 16, the adapter band may be madeof a low or non-conductive material since the metal of lead 4 throughgroove 23 is rendered accessible to solder regardless of theconductivity of the adapter member. Accordingly, the adapter member maybe formed of sheet steel, or, if desired, may be of insulating material,such as nylon, pressed as a finished piece or die cast in place.Furthermore, if a suflicient mass of metal is present within thecrimping region without the additional metal afforded by the adaptermember, the end of the conductor alone can be cold-formed by the dies tothe desired configuration.

We claim:

1. A member of sheet material for conforming electrical component leadsof various diameters to a standardized printed circuit board holecomprising a U-shaped ferrule-forming portion including a trough forreceiving the lead and a pair of ears extending from opposed sides ofthe trough and adapted to be bent into tight engagement with the lead,said ears along their length along the trough decreasing in heightrelative to the bottom of the trough to provide top edges inclined inthe same direction toward the bottom of said trough, said memberincluding a lead-in portion extending forwardly of and beingsubstantially narrow than said trough and ears providing a taperedlead-in point for the end portion of the lead upon insertion with saidmember into a circuit board hole.

2. A member as set forth in claim 1 wherein said top edges are inclineddownwardly toward the end of said trough opposite to said lead-inportion.

References Cited by the Examiner UNITED STATES PATENTS 2,748,452 6/1956Pierce 29l93.5 2,778,097 l/1957 Berg 29l93.5 2,908,887 10/1959 Broske29--193.5

DAVID L. RECK, Primary Examiner.

HYLAND BIZOT, Examiner.

1. A MEMBER OF SHEET MATERIAL FOR CONFORMING ELECTRICAL COMPONENT LEADSOF VARIOUS DIAMETERS TO A STANDARDIZED PRINTED CIRCUIT BOARD HOLECOMPRISING A U-SHAPED FERRULE-FORMING PORTION INCLUDING A TROUGH FORRECEIVING THE LEAD AND A PAIR OF EARS EXTENDING FROM OPPOSED SIDES OFTHE TROUGH AND ADAPTED TO BE BENT INTO TIGHT ENGAGEMENT WITH THE LEAD,SAID EARS ALONG THEIR LENGTH ALONG THE TROUGH DECREASING IN HEIGHTRELATIVE TO THE BOTTOM OF THE TROUGH TO PROVIDE TOP EDGES INCLINED INTHE SAME DIRECTION TOWARD THE BOTTOM OF SAID TROUGH, SAID MEMBERINCLUDING A LEAD-IN PORTION EXTENDING FORWARDLY OF AND BEINGSUBSTNTIALLY NARROW THAN SAID TROUGH AND EARS PROVIDING A TAPEREDLEAD-IN POINT FOR THE END PORTION OF THE LEAD UPON INSERTION WITH SAIDMEMBER INTO A CIRCUIT BOARD HOLE.